21290445 has 72 divisors (see below), whose sum is σ = 42513120. Its totient is φ = 10147680.

The previous prime is 21290441. The next prime is 21290447. The reversal of 21290445 is 54409212.

21290445 is a `hidden beast` number, since 212 + 9 + 0 + 445 = 666.

It is not a de Polignac number, because 21290445 - 2² = 21290441 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21290441) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 360826 + ... + 360884.

It is an arithmetic number, because the mean of its divisors is an integer number (590460).

Almost surely, 2^21290445 is an apocalyptic number.

It is an amenable number.

21290445 is a deficient number, since it is larger than the sum of its proper divisors (21222675).

21290445 is an frugal number, since it uses more digits than its factorization.

21290445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99 (or 78 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21290445 is about 4614.1570194349. The cubic root of 21290445 is about 277.1585281185.

Adding to 21290445 its reverse (54409212), we get a palindrome (75699657).

The spelling of 21290445 in words is "twenty-one million, two hundred ninety thousand, four hundred forty-five".